This invention relates to positioning and load bearing pads on fuel ducts for liquid metal cooled nuclear reactor fuel assemblies, especially for sodium cooled nuclear reactor fuel assemblies.
Fuel assemblies for nuclear reactors may be enclosed within a duct which serves to direct coolant flow through the fuel assembly. The fuel assemblies of the reactor are typically arranged in a grouping called the reactor core, which may contain hundreds of fuel assemblies. The array of fuel assemblies may cause adjacent fuel assembly ducts to abut on one another or surfaces of a core support grid. The fuel assembly duct may be provided with load pad structure, perhaps with a specially hardened surface, to bear contact between adjacent ducts or between ducts and a support grid. Such load pad is intended to endure chaffing and perhaps establish a desired clearance between ducts.
In current designs, the load pads are either welded to the ducts or are integral to the duct walls. The ducts are usually built of 316 stainless steel. As a result of radiation induced swelling, the useful life of a duct is limited to about three reactor fuel cycles. In an effort to extend duct life the use of ferritic steel for the ducts is being considered with the consequence that process steps used to form welded or integral load pads have become extremely difficult.
It is therefore desired to provide a load pad which is not welded or integral to the fuel assembly duct.